Manufacture of artificial silk



i No Drawing.

UNITED STATES PATENT OFFICE.

MANUFACTURE OF ARTIFICIAL SILK.

T 0 all whom it may concern:

Be it known that I, EMILE BRONNERT, a citizen of the Republic of France, residing at 1 Quai du Barrage. in Miilhausen, Alsace- Lorraine, France, haveinvented certain new and useful Improvements in the Manufacture ofArtificial Silk (for which I have filed application in Germany, filed January 23rd, 1919: France, England, Italy, Austria, Hungary, Spain, Switzerland, Norway, Checho- Slovakia. Netherlands, and Denmark, filed February 27th, 1920; Sweden, filed March 2nd. 1920; Bel ium, filed Mar. 3rd, 1920; Finland, filed hfarch 12th. 1920, and Poland, filed March 21, 1920,) of which the following is a specification.

This invention has reference to the manufacture of very fine threads of artificial silk from a raw viscose solution. In the manufacture of such threads by the draw-spinning process it has been found that the higher the acid concentration employed in the coagulating bath. the finer will be the threads produced. This has been recognized as the most essential condition for attaining the requisite fineness, whereas the sulfate contained in the bath has merely a lesser influence. In contra-distinction to the requirements as to the sulfate with coarser threads, it has been found that it is not even advantageous to increase the concentration of the same to too high a degree.

A possible explanation of this remarkable fact is that the viscose, upon issuing from the nozzle, has the tendency, caused by its own superficial tension. to form globular drops. On seizing and drawing out thls drop the coagulating power, inherentin the coagulating bath, acts upon the thread. and renders it more capable of being drawn out the smaller the superficial area the thread presents for attack, that is to say, the thread will be all the finer the smaller said area.

Consequently, the acid must have a higher concentration in order that the skin thus formed, in spite of its small surface, may

have a sufficient tensile strength to permit of winding it off without thread breakage, as is the case of a coarser thread drawn with a lower degree of acid concentration.

The proportion of the precipitant or coagulating power (acid concentration) which is necessary With various thread sizes has been found to be approximately inversely proportional to the square root of the thread size.

Specification of Letters Patent.

ple 1.

Patented Oct. 11, 1921.

Application filed July 10, 1920. Serial No. 395,350.

Thus suitable salt baths such as bisulfates,

sulfates, chlorids, nitrates, etc., of the fixed and volatile alkalis or earth alkalis or mixtures of these with a percentage of 250 gr. sulfuric acid with the sulfate, and with a corresponding feed of "iscose gives a single thread of about two deniers with nozzle openings of 0.10 mm. while a bath, containing 350 gr. sulfuric acid, under similar circumstances. permits threads as low as one denier being drawn out.

, Example 1.

threads of single measure 7.5 deniers.

Example 2. A bath of 360 gr. sodium sulfate to the liter is provided, containing 170 to 190 gr. sulfuric acid. The same viscose is then passed into a solution again of 20 threads,

but of 4 deniers only. The threads can be drawn off smoothly out of similar openings of 0.10 millimeters, as set forth in Exam- Ea'amplc 3.

A solution of 360 sodium sulfate to the liter is provided, which, at the same time contains 250 to 280 gr. sulfuric acid, and the I viscose is delivered to it in measured quantities again of 20 threads, but in this case of only 2 deniers. The highly concentrated sulfuric acid mass in this case permits the threads "to be smoothly drawn off out of openings of 0.10 millimeters. A suitable temperature for the bath is from 40 to,50 degrees cent-igrade. I V

The sodium sulfate can be replaced iii a well-known manner, either wholly or in part through other soluble sulfates. The production of thread is not changed when somewhat weakened masses of sulfate or other salts are employed.

The particular feature of the invention resides in the concentration of the acid, rather than in the proportion of the salts employed.

\Vhat I claim is:

1. A step in the process of making artificial silk which permits of predetermining the fineness the thread to be produced, which compri es treating viscose in a coag u lating bath containing a salt and an acid, the proportion of the latter to the whole being approximately inversely proportional to the square root of the thread size.

2. A step in the process of making artifi cial silk which permits of predeterminin the fineness of the thread to be produce WhlCh 'comprisestrea-ting viscose in a coaguv lating bath containing sodium sulfate and sulfuric acid, the proportion of, the latter to the whole being, approximately inversely proportional to the square root of the thread size.

In witness whereof Ihave hereunto signed my name.

EMILE BRONNER-T.

Witnesses:

HENRY BBONNEBT, RALPH BRONNERT. 

